Side plates (4) each include a base portion (41), in contact with fins (11), and side wall portions (42) extending from the base portion (41) in the direction Y in which tubes (10) are stacked. The side wall portions (42) are formed with a bent deforming portion (421) to facilitate extension/shrinkage, of the side wall portions (42), in the longitudinal direction (X) of the tubes (10). The base portion (41) is formed with a pair of hooks (411) extending toward the surface of the bent deforming portion (421) in opposed relation to the base portion (41). In the case where the base portion (41) tends to be displaced, the hooks (411) come into contact with the bent deforming portion (421) to thereby suppress or prevent the displacement of the base portion (41).